1. Field of the Invention (Technical Field)
The present invention relates to methods and apparatuses to control antenna polarization states.
2. Description of Related Art
Multiple polarization antennas are typically implemented through a conjunction of either electrical or mechanical switching, electrical or mechanical attenuation, electrical or mechanical phase shifting, and dedicated transmission line routing definitions. Digital post-processing software may also be employed to provide a virtual sense of polarization diversity. Mechanical switches degrade over time and have limited high frequency application while high frequency electrical switches are relatively expensive. Digital electronic phase shifters are able only to adjust the phase in discrete increments, resulting in polarization degradation, while predictable electronic control of analog phase shifters is difficult to implement while remaining relatively expensive. Attenuators reduce the RF efficiency of the entire concept by “throwing away” RF power to achieve the desired power balance between the orthogonal ports. The drawback of using software is that the answer is not “real time” and requires significant effort to design a flexible software/hardware interface. The present invention eliminates the discrete switch and phase shifter requirements by means of a low cost, monolithic, integrated collection of simple transmission lines controlled by means of variable dielectric.